Process for treating water-soluble organic wastes

ABSTRACT

A process for treating a waste feed stream containing essentially water-soluble organic wastes, in particular those originating in refinery reservoirs, refinery waste streams, refinery pits, and lube oil additive plants, is described as involving heating the stream under turbulent flow conditions to temperatures of 400* to 700*F and pressures of 300 to 3,100 psi in the presence of air or of oxygen thereby splitting off carbon dioxide. The oxidized waste stream, which has a considerably reduced chemical oxygen demand, is continuously fed to a hot contacting zone and is in heat-exchange relationship with the incoming effluent stream.

0 United States Patent 1 3,772,181 Cole et a1. Nov. 13, 1973 PROCESS FORTREATHNG 3,449,247 6/1969 Bauer 210/63 WATER-SOLUBLE QRGANEC WAsTESFOREIGN PATENTS OR APPLICATIONS Inventors: Edward 114-13012, Fishkill;Howard 1,074,391 1/1960 Germany 23/48 Hess, Glenham, both of N .Y.

[73] Assignee: Texaco Inc., New York, NY. Primary Examiner MichaelRogers Attorney-Thomas H. Whaley et a1.

[22] FIled: Oct. 27, 1971 [63] Continuation-impart of Ser. No. 866,215,Oct. 14, 1969, Pat. No. 3,642,620, and a continuation-in-part of Ser.No. 780,080, Nov. 29, 1968, Pat. No. 3,507,788.

[52] US. Cl. 210/63, 210/71 [51] Int. Cl. (302C 5/04 [58] Field ofSearch ..210/12,15, 63, 71

[56] References Cited UNITED STATES PATENTS 2,824,058 2/1958 Zimmermann210/63 DISCHARGE WASTE STREAM [57] ABSTRACT A process for treating awaste feed stream containing essentially water-soluble organic wastes,in particular those originating in refinery reservoirs, refinery wastestreams, refinery pits, and lube oil additive plants, is described asinvolving heating the stream under turbulent flow conditions totemperatures of 400 to 700F and pressures of 300 to 3,100 psi in thepresence of air or of oxygen thereby splitting off carbon dioxide. Theoxidized waste stream, which has a considerably reduced chemical oxygendemand, is continuously fed to a hot contacting zone and is inheat-exchange relationship with the incoming effluent stream.

10 Claims, 1 Drawing Figure PAIENTEDnnv 13 ms 3.7721 81 DISCHARGE WASTESTREAM AIR 22 PROCESS FOR TREATING WATER-SOLUBLE ORGANIC WASTES CROSSREFERENCE TO COPENDING APPLICATIONS This application is acontinuation-in-part of our commonly assigned application Ser. No.866,215 filed Oct. 14, 1969, now U.S. Pat. No. 3,642,620, itself acontinuation-in-part of our commonly assigned U.S. application Ser. No.780,080 filed Nov. 29, 1968, and now U.S. Pat. No. 3,507,788.

FIELD oI= INVENTION This invention relates to a continuous process forthe treatment of discharge water contaminated by watersoluble organiccompounds by oxidizing these compounds in the liquid phase in thepresence of oxygen under autogenous pressure and turbulent flowconditions.

DESCRIPTION OF THE PRIOR ART The main objects of processes for thetreatment of waste streams is to produce a sterile, non-putresciblesolid residue which can be separated later from the effluent as well asan effluent which is unobjectionable for final disposal. Y I

A number of methods have been developed for reducing the chemical oxygendemand (COD) of effluent industrial wastes such as biological sludgesfrom chemical and pharmaceutical plants. Among such methods are the wetair oxidation and the activated sludge digestion processes'ln theactivated sludge processes, organic sludge is subjected to anaerobic andaerobic bacterial action or both. In the wet air oxidation processes, anaqueous slurryof sludge is subjected to oxidation with air at elevatedtemperature and pressure.

In a newer process, raw primary activated sludge having a chemicaloxidation demand of the order of 40 grams of oxygen per liter isoxidized batchwise with the aid of steam injection under relativelyquiescent conditions in heavy, thick-walled reactors at around 525F. and1,750 psig. These reactors are charged once every 24 hours and reducethe chemical oxidation demand of the effluent liquid to around g/l or byabout 75 percent. I Y

All the above outlined processes basically only concentrate the sludgeso that it can be disposed of more rapidly; are relatively costly andadditionally, the conditions under which they are carried out are notsevere enough to dispose of very stable and resistant contaminants suchas maleic acid, fumaric acid, phthalic acid, terphthalic acid and thelike. Currently, these are handled by bacterial oxidation in ponds butthis requires considerable land to hold the waste stream and is slow.

OBJECTS AND SUMMARY OF THE INVENTION The main object of this inventionis to provide an ecnatural water systems containing marine life withoutany biological treatment.

In the process of the present invention whereby the foregoing objectsare attained, a waste feed stream containing essentially water-solubleorganic wastes is continuously subjected to non-catalytic air oxidationat a temperature in the range of 400 to 700F. at a pressure within therange of 300 to 3,100 psi under turbulent conditions for a contact timeranging from 0.1 minutes to 2 hours whereby substantially all theorganic wastes are oxidixed to carbon dioxide and water.

DESCRIPTION The process of this invention will be better understood byreferring to the accompanying FIGURE illustrating diagrammatically apreferred embodiment of the present invention as applied to thetreatment of a waste stream from a waste refinery reservoir.

With reference to the FIGURE, a waste feed stream containing theabove-mentioned acids is pumped by pump 10 through line 11 into heatexchanger 12 in which its temperature is increased by contact with hotoxidized effluent on its way to be discharged through line 24. The wastefeed stream passes through mix valve 116 where compressed air oroxygen'at system pressure is sparged into the stream and flowsconcurrently therewith through line 18, and tubular coil 20 in firedheater 22. Turbulent flow conditions are thus imparted to the waste feedstream so thatintimate contact between the stream and the air or oxygenis achieved, to bring about oxidation of the dissolved organic materialswith formation of carbon dioxide. By analogy with concurrent heattransfer studies between immiscible fluids it can be postulated that anoptimum theoretical contacting stage is less than 4 feet. Consideringthat' satisfactory COD reduction required three such contacting stagesor coils, this can be done in a 12 foot coil which can be heated inalready existing facilities such as an incinerator heater box.

A suitable temperature range to which the waste feed stream must beheated is 500 to 700F. The temperature at which the process operates isimportant because of compression costs. Generally the pressure isslightly above the vapor pressure of water for the efflu t stream, whichplaces it in the range of 300 to 3,10013si. In practice the pressure isset by a back pressure regulator (not shown) at a point slightly abovethe vapor pressure of water at the given temperature. Theinterrelationship between temperature pressure and the solubility ofoxygen in water is well known and the temperature and pressure rangesabove given insure that the oxygen will be dissolved in the aqueousphase of the waste feed stream and hence in intimate contact with thedissolved organic material. Use of oxygen or of air enriched with oxygenallows operation of the process at temperatures and pressures below theranges given above.

As shown in the FIGURE, the oxidized effluent passes through the heatexchanger where it heats the waste feed stream and then through apressure reducing valve 26 before being discharged through line 28.

The flow of liquid and air or oxygen in the tubular reactor should beturbulent and for a given tube reactor the type of flow depends on thequantity of fluid flowing through the reactor. Turbulent flow isdesirable for better contact between air and organic matter with theresult that better conversion of the organic matter to CO and water willbe obtained. A useful relationship that substantially indicates the typeof flow in a tube is the Reynolds number. The Reynolds number is definedN (DV/p.)rr where:

N Reynolds number D Inside Diameter of tube, ft

V Average linear velocity, ft/sec 11 Fluid density, lb/cu ft p. Fluidviscosity, lb/(ft) (sec) Preferably Reynolds numbers above 4000 shouldbe maintained in the tubular reactor. The tubular reactor suitably hasan internal diameter within the range of one half to 4 inches. Thelength of the reactor tube is preferably such that the average residencetime of liquid in the tube is at least one minute. The air pressuresupplied should be slightly above the vapor pressure of the system atoperating temperature so that the waste stream is maintainedsubstantially in the liquid phase. Generally, it is desirable to operatethe heating step so that the pressure at the outlet from the tubularreactor is near or only slightly greater than the vaporizationtemperature of water at the reactor outlet. To conserve heat, it isgenerally desirable to maintain the pressure at the outlet of thetubular heating zone higher than the vapor pressure of water at theoutlet temperature of the heating zone.

While the above description represents the preferred mode of carryingout the claimed process, it will be appreciated that the same isamenable to various modifications. Thus, the air or the oxygen could beadded at different or multiple points in the system. Depending upon theprecise nature of the organic waste materials, it might be better to addthe oxidant to the effluent waste stream before the heat exchanger oragain it might be necessary to add additional oxidant within or into theheater coil.

In a modification of the present process, the oxidized effluent whilestill under system pressure is let down through conventional pressurerecovery equipment so that its energy can be recovered to pump up thewaste feed stream to system pressure.

In a further modification of the invention, the pressure of the oxidizedeffluent is let down through conventional pressure recovery equipmentand used to supply energy for compressing the oxidant gas.

In the following examples, and throughout the present specification, theterm chemical oxygen demand, abbreviated COD, is used in its usual senseof denoting the total oxidizable material present in the liquid underconsideration regardless of whether or not it is biodegradable. The termBOD" denotes the amount of oxygen consumed during a 5-day period ofbacterial activity at C. on a chemically standardized and stabilizedsample; while COD is not strictly comparable to the Biological OxygenDemand (BOD) it is useful as an indication of reduction of BOD to give abasis for comparison of the effectiveness of alternate methods oftreatment, particularly when applied to comparable waste samples.

Typical of the soluble organic compounds that may be in the wastes whichmay be treated by the process of the invention at any particular timeare;

l. Alcohols; e.g. propanol, ethylene glycol, phenol.

2. Ethers; e.g. diethyl ether, ethylene oxide.

3. Carbonyl (C 0) Compounds; e.g. butyraldehyde, methyl ethyl ketone,ethyl acetate, biacetyl, lactic acid, alanine 4. Carbohydrates; e.g.D-glucose 5. Derivatives of NH e.g. methyl amine, ethylene diamine, etc.

6. Amides; e.g. N-methyl pyrrolidone etc.

7. Amino acids; e.g. alanine.

8. Lactams; e.g. 'y-butyrolactam.

As disposal pits and reservoirs handle both wastes from oil and chemicalprocessing the water soluble compounds may include any one or all of thetypes of compounds cited above.

EXAMPLE 1 A total waste stream from a refinery reservoir was found tohave a relatively low COD of 300. This COD was reduced to 148 byoxidizing at 400F in the apparatus shown in the drawing. However, bytreating the stream according to the invention at 450F. and injectingair at 500 psig, the COD was reduced to 62.

Repeating the process just given but at 500F. reduced the COD to 40which is a value entirely acceptable for discharge into any body ofwater.

EXAMPLE 2 An overflow stream from a disposal pit had a COD of 2,900.This stream was oxidized by the method of the invention in three stagesat 500F. using air at 500 psig and had its COD reduced to 718 or areduction of percent.

EXAMPLE 3 Bottoms from a methanol tower from lube oil additivemanufacture were found to have a high COD (61 ,500). One stage oftreatment by the process of the invention involving burning at 600F.with air reduced the COD to 11,450, a reduction of 81 percent.

It will be appreciated that the actual composition of the streams whichcan be successfully treated by the claimed process is not critical. CODreduction will take place as long as the stream treated containsessentially water-soluble organic materials.

We claim:

1. A process for treating an aqueous waste feed stream containingessentially water-soluble organic wastes comprising continuously passingsaid stream into and through at least one hot contacting zone, injectingan oxygen-containing gas in said stream dissolving oxygen in said streamby applying thereto turbulent flow conditions characterized by aReynolds number greater than 2,000 and subjecting said stream while insaid zone to non-catalytic air oxidation at a temperature rangingbetween about 400 and 700F. at a pressure above the vapor pressure ofwater for the aqueous waste feed stream and ranging from about 300 to3,100 psi so that the oxygen is dissolved in the aqueous phase of thewaste feed stream and hence in intimate contact with the dissolvedorganic wastes for between about 0.1 minutes and about 2 hours toproduce an effluent stream wherein substantially all the organic wastesare oxidized to carbon dioxide and water.

2. The process according to claim 1 wherein said effluent stream is inheat exchange relationship with said waste feed stream.

3. The process according to claim 1 wherein said waste feed stream isthe aqueous effluent from a refinery reservoir.

4. The process according to claim 1 wherein an oxidizing gas is spargedinto said waste stream and caused to flow concurrently therewith throughsaid contacting zone.

5. The process according to claim 1 wherein an oxidizing gas is added tothe waste stream before the stream is heated.

6. The process according to claim 1 wherein a pressurized oxidizing gasis added to said waste stream.

7. The process according to claim 1 wherein an addi

2. The process according to claim 1 wherein said effluent stream is inheat exchange relationship with said waste feed stream.
 3. The processaccording to claim 1 wherein said waste feed stream is the aqueouseffluent from a refinery reservoir.
 4. The process according to claim 1wherein an oxidizing gas is sparged into said waste stream and caused toflow concurrently therewith through said contacting zone.
 5. The processaccording to claim 1 wherein an oxidizing gas is added to the wastestream before the stream is heated.
 6. The process according to claim 1wherein a pressurized oxidizing gas is added to said waste stream. 7.The process according to claim 1 wherein an additional amount of saidoxidizing gas is added to said stream as said stream is heated.
 8. Theprocess according to claim 1 wherein the pressure of said effluentstream is recovered and used to pump up said waste feed stream.
 9. Theprocess according to claim 1 wherein the pressure of said effluentstream is recovered and used to compress said oxidizing gas.
 10. Theprocess according to claim 1 wherein said waste stream is a waste streamfrom a lube oil additive plant.